The Question:

What is the approximate Jewish population in the United
States?

The Answer:

According to the Jewish
Virtual Library, there were an estimated 6,452,030 Jewish
people in the United States
in 2006 (the most recent data available), which is more than there
were in any other country. (Israel came in second.) This represents
approximately 2.2% of the total U.S. population.

The same site has a
chart of the state-by-state breakdown of the Jewish
population, revealing that New York had both the highest number
(1,618,320) and highest percentage (8.4%) of Jews in the country, by a
wide margin.